1. Field of the Invention
The present invention relates generally to the detection and determination of an event characteristic and, more particularly, to detecting and determining one or more characteristics of an event, such as, for example, the material failure of a monitored component.
2. State of the Art
It is often desirable to detect and determine various event characteristics associated with the physical response or reaction of a given component or material when subjected to various influences such as, for example, an application of a force or exposure to a specific environment for a given period of time. It is desirable to determine the response of such a component so as to accurately predict future behavior and to properly design systems and components which react and perform in a predictable manner.
For example, material testing is often performed to determine mechanical behavior of a specific material or a particular component configuration under specified conditions. Such behavior might include the determination of, for example, yield strength, fracture toughness, impact strength, fatigue limits, temperature-induced effects, corrosion or degradation rates, crack rate propagation or any of a number of other mechanical, material or physical properties.
In a more particular example, fracture tests are conventionally conducted to determine the fracture energy of an adhesive bond. One such fracture test is known as a tapered double cantilevered beam (TDCB) test. As shown in FIG. 1, a TDCB test involves a test specimen 100 having an adhesive bond 102 between two similarly configured tapered beams 104 and 106. A force “F” of known magnitude is applied to each beam 104 and 106 so as to pull the beams 104 and 106 in opposing directions. The resulting structure thus includes two beams 104 and 106 loaded in a cantilevered manner. The force F applied to the beams 104 and 106 is ultimately transferred into the adhesive bond 102, which is then monitored for material failure which manifests itself through propagation of a crack.
Conventional means of monitoring the adhesive bond 102 for failure include visual inspection and/or use of electronic equipment including, for example, one or more resistive-type propagation gages adhered to the location of interest (e.g., adjacent the adhesive bond 102) and electrically coupled to a data acquisition system. Such conventional means of monitoring the adhesive bond are labor intensive and, particularly when utilizing electronic equipment, involve considerable expense. Furthermore, such conventional means are not highly efficient. For example, if a testing specimen becomes unstable, a crack may propagate at a very high rate approaching the speed of sound for the given material being tested. In such a circumstance, it becomes impossible to obtain useful information about the crack propagation by way of visual inspection.
On the other hand, when using conventional electronic monitoring equipment, data is continuously collected over time and sample rates of up to several megahertz are required for accurate data acquisition. Thus, if a testing specimen fails over a period of time which is in excess of, for example, twenty minutes, the acquired data will include several billion data points for subsequent processing and analysis. Storing such a large amount of data wastes valuable memory or storage space since only a few of the collected data points are actually relevant and desirable for purposes of proper fracture analysis.
Additionally, as alluded to above, the cost associated with the equipment capable of sampling and recording such a large number of data points may often be prohibitive. For example, an individual resistive-type propagation gage may cost $300 (and isn't reusable) while the data acquisition equipment having an adequate sample rate may cost $8,000–$10,000 or more.
In view of the shortcomings in the art, it would be advantageous to provide an apparatus and method for determining event characteristics, such as, for example, acquiring data relative to a material or component failure, which is simple in its operation and configuration, highly efficient and relatively inexpensive.